1. Field of the Disclosure
This disclosure relates generally to an apparatus and method for extracting heat from downhole devices and more particularly to extracting heat using core-shell nano particles.
2. Background of the Art
Wellbores are drilled in subsurface formations for the production of hydrocarbons (oil and gas). Wells often extend to depths of more than 1500 meters (about 15,000 ft.). Many such wellbores are deviated or horizontal. After a wellbore is formed, a casing is typically installed in the wellbore, which is perforated at hydrocarbon-bearing formation zones to allow the hydrocarbons to flow from the formation into the casing. A production string is typically installed inside the casing. The production string includes a variety of flow control devices and a production tubular that extends from the surface to each of the perforated zones. Some wellbores are not cased and in such cases the production string is installed in the open hole. Often, the pressure in the hydrocarbon-bearing subsurface formations is not sufficient to cause the hydrocarbons to flow from the formation to the surface via the production tubing. In such cases, one or more electrical submersible pumps (ESP) are deployed in the wellbore to lift the hydrocarbons from the production tubing to the surface. Power to the ESPs is supplied from the surface. Such pumps are often deployed at great depths, where the wellbore temperature can exceed 200° F. An ESP includes an electrical motor and a pump. The electrical motor includes magnets and windings, which generate heat. The temperature inside the motor of an ESP can often reach or exceed 300° C. ESP's are relatively expensive and can therefore also be prohibitively expensive to replace. It is therefore desirable to extract as much heat as practicable to reduce the temperature of the motor for efficient operation and the longevity of the motor. Other downhole devices and sensors also operate more efficiently and have longer operating lives at lower temperatures.
The disclosure herein provides apparatus and methods for removing or extracting heat from downhole devices including, but not limited to, electrical submersible pumps.